Open ChayimFriedman2 opened 1 month ago
WG-prioritization assigning priority (Zulip discussion).
In #126578 the perf. triaging showed some regression in binary size (though not entirely due to that patchset). Probably this is another side effect.
@rustbot label -I-prioritize +P-medium
The root cause is a bug in LLVM: https://github.com/llvm/llvm-project/issues/101899.
In the process of trying to stabilize
get_many_mut()
, and while trying to check what will be the costs of a more detailed error type, I came across the following perf regression from stable to beta.Code
I tried this code:
On stable (with
RUSTC_BOOTSTRAP=1
) this optimizes nicely to the following code (https://godbolt.org/z/zq8EG7df7):However, on beta (and nightly) this adds a whole bunch of unnecessary instructions:
With
cargo-bisect-rustc
I bisected it to https://github.com/rust-lang/rust/pull/126578. CC @scottmcm.@rustbot label +regression-from-stable-to-beta -regression-untriaged -C-bug +perf-regression +I-heavy +I-slow